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  • AERODYNAMICS  (366)
  • 1980-1984  (366)
  • 1965-1969
  • 1945-1949
  • 1981  (366)
  • 201
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    Performance and loads data from a wind tunnel test of a full-scale, coaxial, hingeless rotor helicopter (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A full-scale XH-59A advancing blade concept helicopter was tested in Ames Research Center's 40 by 80 foot wind tunnel. The helicopter was tested with the rotor on and off, rotor hub fairings on and off, interrotor shaft fairing on and off, rotor instrumentation module on and off, and auxiliary propulsion thrust on and off. An advance ratio range of 0.25 and 0.45 with the rotor on and from 60 to 180 knots with the rotor off was investigated. Data on aerodynamic forces and moments, rotor loads, rotor control positions and vibration for the XH-59A as well as the aerodynamic performance of the isolated rotor are presented.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81329 , A-8732 , USAAVRADCOM-TR-81-A-27
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  • 202
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    Comparison of experimental and theoretical turbulence reduction characteristics for screens, honeycomb, and honeycomb-screen combinations (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Turbulence reduction research using screens, honeycomb, and combinations thereof was conducted in a half-scale model of a portion of the Langley 8-foot transonic pressure tunnel. It was found that screens alone reduce axial turbulence more than lateral turbulence; whereas, honeycomb alone reduces laterial turbulence more than axial turbulence. Because of this difference, the physical mechanism for decreasing turbulence for screens and honeycomb must be completely different. It is concluded that honeycomb with a downstream screen is an excellent combination for reducing turbulences.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1958 , L-14628
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  • 203
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    Stability and control characteristics of a monoplanar missile configuration with triform-tail-fin arrangements at Mach numbers from 1.70 to 2.86 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A wind-tunnel missile model with either a lower vertical tail fin with a pair of horizontal fins having 0 deg, 22.5 deg, or 30 deg dihedral or an upper vertical tail fin with horizontal fins having 0 deg, -22.5 deg, or -30 deg dihedral was investigated. The results indicated that those configurations with horizontal fins at or below the horizontal plane had nearly linear pitching-moment characteristics, while those with the horizontal fins above the horizontal plane experienced pitch-up which increased with increasing horizontal-fin-dihedral angle. At zero angle of attack, the configurations were directionally stable at most test Mach numbers. Generally, those configurations with the upper vertical fin had positive effective dihedral at zero angle of attack, while those with he lower vertical fin had negative effective dihedral. For roll control, three deflected tail fins produced more total roll control than two horizontal fins. For yaw control, three tail fins deflected equally or differentially produced more total yaw control than the single vertical fin.
    Keywords: AERODYNAMICS
    Type: NASA-TM-83223 , L-14724
    Format: application/pdf
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  • 204
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    A pulse-forming network for particle path visualization (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A procedure is described for visualizing nonsteady fluid flow patterns over a wide velocity range using discrete nonluminous particles. The paramount element responsible for this capability is a pulse-forming network with variable inductance that is used to modulate the discharge of a fixed amount of electrical energy through a xenon flashtube. The selectable duration of the resultant light emission functions as a variable shutter so that particle path images of constant length can be recorded. The particles employed as flow markers are hydrogen bubbles that are generated by electrolysis in a water tunnel. Data are presented which document the characteristics of the electrical circuit and establish the relation of particle velocity to both section inductance and film exposure.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81311 , A-8671 , AVRADCOM-TR-81-A-21
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  • 205
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    Description and calibration of the Langley unitary plan wind tunnel (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The two test sections of the Langley Unitary Plan Wind Tunnel were calibrated over the operating Mach number range from 1.47 to 4.63. The results of the calibration are presented along with a a description of the facility and its operational capability. The calibrations include Mach number and flow angularity distributions in both test sections at selected Mach numbers and tunnel stagnation pressures. Calibration data are also presented on turbulence, test-section boundary layer characteristics, moisture effects, blockage, and stagnation-temperature distributions. The facility is described in detail including dimensions and capacities where appropriate, and example of special test capabilities are presented. The operating parameters are fully defined and the power consumption characteristics are discussed.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1905 , L-14024
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  • 206
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    Low Reynolds number airfoil survey, volume 1 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The differences in flow behavior two dimensional airfoils in the critical chordlength Reynolds number compared with lower and higher Reynolds number are discussed. The large laminar separation bubble is discussed in view of its important influence on critical Reynolds number airfoil behavior. The shortcomings of application of theoretical boundary layer computations which are successful at higher Reynolds numbers to the critical regime are discussed. The large variation in experimental aerodynamic characteristic measurement due to small changes in ambient turbulence, vibration, and sound level is illustrated. The difficulties in obtaining accurate detailed measurements in free flight and dramatic performance improvements at critical Reynolds number, achieved with various types of boundary layer tripping devices are discussed.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165803-VOL-1
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  • 207
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    Pressure distributions and shock shapes for 12.84 deg/7 deg on-axis and bent-nose biconics in air at Mach 6 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Pressure distributions and shock shapes on a spherically blunted, 12.84 deg /7 deg on axis biconic and a spherically blunted, 12.84 deg/7 deg bent nose biconic at Mach 6 in air were measured. The angle of attack, referenced to the axis of aft cone, was varied from 0 deg to 25 deg in nominal 5 deg increments. Two values of free stream Reynolds number based on model length were tested. Predictions from simple, theories and from a supersonic, three dimensional, external invsicid code (STEIN) are compared with measured values. Predicted STEIN shock shapes and windward pressures are in agreement with measured values for both biconics over the present range of angle of attack.
    Keywords: AERODYNAMICS
    Type: NASA-TM-83222 , L-14896
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  • 208
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    Force and moment, flow-visualization, and boundary-layer tests on a shuttle orbiter model at Mach 6 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Force and moment, flow visualization, and boundary layer state tests were conducted using two 0.004 scale shuttle orbiter models. The force and moment tests were conducted for an angle of attack range from 20 to 40 deg and for Reynolds numbers based on reference length from 0.4 million to 3.6 million. Schlieren photographs were obtained for each angle of attack and Reynolds number. The boundary layer state tests, which were conducted using hot film sensors mounted in a separate model, were conducted over the same range of conditions as the force tests. Test results were combined to show that changes in the boundary layer on a typical hypersonic force test model affect measurement of the axial force coefficient and that the state of the local boundary layer is important for interpreting hypersonic aerodynamic test results.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1952 , L-14782
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  • 209
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    A vortex-filament and core model for wings with edge vortex separation (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A method for predicting aerodynamic characteristics of slender wings with edge vortex separation was developed. Semiempirical but simple methods were used to determine the initial positions of the free sheet and vortex core. Comparison with available data indicates that: the present method is generally accurate in predicting the lift and induced drag coefficients but the predicted pitching moment is too positive; the spanwise lifting pressure distributions estimated by the one vortex core solution of the present method are significantly better than the results of Mehrotra's method relative to the pressure peak values for the flat delta; the two vortex core system applied to the double delta and strake wing produce overall aerodynamic characteristics which have good agreement with data except for the pitching moment; and the computer time for the present method is about two thirds of that of Mehrotra's method.
    Keywords: AERODYNAMICS
    Type: NASA-CR-164980 , CRINC-FRL-424-1
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  • 210
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    Aerodynamic measurements concerned with a turret model (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation was carried out in the 14 by 14 ft Ames transonic wind tunnel on a turret model. The aerodynamic parameters measured were steady and unsteady pressures (static and total fluid pressures), local mean velocities, and local mean densities at selected locations along the optical beam path for the azimuth look angles of 90, 120, and 150 degrees from the turret. The test stream Mach numbers considered are 0.55, 0.65 and 0.75, and the Reynolds number per meter is in the range of 10 million. The results indicate that severe optical degradation can be expected at aft look azimuth, angles, this degradation in optical performance increases as the azimuth angle is increased. The ratio of rms static pressure to the local mean static pressure peaks in the range of 0.07 to 0.12 and the ratio of rms total pressure to the local mean total pressure peaks in the range of 0.02 to 0.04. These values depend on the Mach number and the aft look azimuth angle. The scale lengths obtained from correlation considerations are also presented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-166264
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  • 211
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    Subsonic balance and pressure investigation of a 60-deg delta wing with leading-edge devices (data report) (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The drag reduction potential of leading edge devices on a 60 degree delta wing at high lift was examined. Geometric variations of fences, chordwise slots, pylon type vortex generators, leading edge vortex flaps, and sharp leading edge extensions were tested individually and in specific combinations to improve high-alpha drag performance with a minimum of low-alpha drag penalty. The force, moment, and surface static pressure data for angles of attack up to 23 degrees, at Mach and Reynolds numbers of 0.16 and 3.85 x 10 to the 6th power per meter are documented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165806
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  • 212
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    Calculations of transonic potential flow over cascades (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Transonic flow through a cascade was studied by using the full potential equation and the finite volume method of Jameson and Caughey. The C-type computational grid is generated by an electrostatic analogy and simple shearing transformation. The solution algorithm includes an option of using either an artificial density or an artificial viscosity formulation of the dissipative term. Using the developed code, flows through a cascade of NACA 0012 airfoils and flows through a cascade of shockless blades were computed. It is found that the designed flow through the shockless blade is accurately predicted, the artificial density formulation shows more tolerance to the mesh irregularity, and the C-type mesh does not extend very far upstream for a small pitch-cord ratio.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165471 , FRR-182
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  • 213
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    Space shuttle solid rocket booster sting interference wind tunnel test analysis (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Wind tunnel test results from shuttle solid rocket booster (SRB) sting interference tests were evaluated, yielding the general influence of the sting on the normal force and pitching moment coefficients and the side force and yawing moment coefficients. The procedures developed to determine the sting interference, the development of the corrected aerodynamic data, and the development of a new SRB aerodynamic mathematical model are documented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-161885 , TR-230-2042
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  • 214
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    Wind-tunnel results for a modified 17-percent-thick low-speed airfoil section (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Wind-tunnel tests were conducted in the Langley low-turbulence pressure tunnel to evaluate the effects on performance of modifying a 17-percent-thick low-speed airfoil. The airfoil contour was altered to reduce the pitching-moment coefficient by increasing the forward loading and to increase the climb lift-drag ratio by decreasing the aft upper surface pressure gradient. The tests were conducted over a Mach number range from 0.07 to 0.32, a chord Reynolds number range 1.0 x 10 to the 6th power to 12.0 x 10 to the 6th power, and an angle-of-attack range from about -10 deg to 20 deg.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1919 , L-14666
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  • 215
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    Some observations on a new numerical method for solving Navier-Stokes equations (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An explicit-implicit technique for solving Navier-Stokes equations is described which, is much less complex than other implicit methods. It is used to solve a complex, two-dimensional, steady-state, supersonic-flow problem. The computational efficiency of the method and the quality of the solution obtained from it at high Courant-Friedrich-Lewy (CFL) numbers are discussed. Modifications are discussed and certain observations are made about the method which may be helpful in using it successfully.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1934 , L-14746
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  • 216
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    Aircraft wing trailing-edge noise (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The mechanism and sound pressure level of the trailing-edge noise for two-dimensional turbulent boundary layer flow was examined. Experiment is compared with current theory. A NACA 0012 airfoil of 0.61 m chord and 0.46 m span was immersed in the laminar flow of a low turbulence open jet. A 2.54 cm width roughness strip was placed at 15 percent chord from the leading edge on both sides of the airfoil as a boundary layer trip so that two separate but statistically equivalent turbulent boundary layers were formed. Tests were performed with several trailing-edge geometries with the upstream velocity U sub infinity ranging from a value of 30.9 m/s up to 73.4 m/s. Properties of the boundary layer for the airfoil and pressure fluctuations in the vicinity of the trailing-edge were examined. A scattered pressure field due to the presence of the trailing-edge was observed and is suggested as a possible sound producing mechanism for the trailing-edge noise.
    Keywords: AERODYNAMICS
    Type: NASA-CR-164952
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  • 217
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    Analytical and experimental study of flow phenomena in noncavitating rocket pump inducers (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The flow processes in rocket pump inducers are summarized. The experimental investigations were carried out with air as the test medium. The major characteristics features of the rocket pump inducers are low flow coefficient (0.05 to 0.2) large stagger angle (70 deg to 85 deg) and high solidity blades of little or no camber. The investigations are concerned with the effect of viscosity not the effects of cavitation. Flow visualization, conventional and hot wire probe measurement inside and at the exit of the blade passage, were the analytical methods used. The experiment was carried out using four three and two bladed inducers with cambered blades. Both the passage and the exit flow were measured. The basic research and boundary layer investigation was carried out using a helical flat plate (of some dimensions as the inducer blades tested), and flat plate helical inducer (four bladed). Detailed mean and turbulence flow field inside the passage as well as the exit of the rotor were derived from these measurement. The boundary layer, endwall, and other passage data reveal extremely complex nature of the flow, with major effects of viscosity present across the entire passage. Several analyses were carried out to predict the flow field in inducers. These included an approximate analysis, the shear pumping analysis, and a numerical solution of exact viscous equations with approximate modeling for the viscous terms.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3471 , PSU/TURBO-R81-3
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  • 218
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    Flight test evaluation of drag effects on surface coatings on the NASA Boeing 737 TCV airplane (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A flight test program was conducted in which the effects of various surface coatings on aerodynamic drag were investigated; results of this program are described in this report. The tests were conducted at NASA-Langley Research Center on the terminal configured vehicle (TCV) Boeing 737 research airplane. The Boeing Company, as contractor with NASA under the Energy Efficient Transport (EET) program, planned and evaluated the experiment. The NASA-TCV Program Office coordinated the experiment and performed the flight tests. The principal objective of the test was to evaluate the drag reduction potential of an elastomeric polyurethane surface coating, CAAPCO B-274, which also has been considered for application on transport airplanes to protect leading edges from erosion. The smooth surface achievable with this type of coating held some promise of reducing the skin friction drag as compared to conventional production type aircraft surfaces, which are usually anodized bare metal or coated with corrosion protective paint. Requirements for high precision measurements were the principal considerations in the experiment.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165767 , NAS 1.26:165767 , D6-37256-REV
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  • 219
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    Wind tunnel force and pressure tests (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Force and surface pressure distributions were measured for a 13% medium speed (NASA MS(1)-0313) airfoil fitted with 20% aileron, 25% slotted flap and 10% slot lip spoiler. All tests were conducted in the Walter Beech Memorial Wind Tunnel at a Reynolds number of 2.2 million and a Mach number of 0.13. Results include lift, drag, pitching moments, control surface normal force and hinge moments, and surface pressure distributions. The basic airfoil exhibits low speed characteristics similar to the GA(W)-2 airfoil. Incremental aileron and spoiler performance are quite comparable to that obtained on the GA(W)-2 airfoil. Slotted flap performance on this section is reduced compared to the GA(W)-2, resulting in a highest c sub l max of 3.00 compared to 3.35 for the GA(W)-2.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3439 , NAS 1.26:3439 , WSU-AR-78-4
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  • 220
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    Three-dimensional separated flows past ground vehicles (1981)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The separated flow past a thick body is calculated using a theoretical model based on a discrete wake-vortex representation. Rehbach's unsteady inviscid scheme (1977) was used in the three-dimensional analysis. The obstacle is represented by singularities, and the wake is modeled by vortex particles emitted at the separation line. Calculated results for an axisymmetric body are compared with flow visualization results.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75899 , Colloq. d''Aerodynamique Appl.; Nov 13, 1979 - Nov 15, 1979; Lille; France
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  • 221
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    Experimental study of the interaction between the wing of a subsonic aircraft and a nacelle of a high by-pass ratio engine (1981)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The oncoming of a new generation of subsonic transport aircraft (with supercritical wing and high by-pass ratio turbofans) led to an experimental study of wing nacelle jet pylon interference in transonic flow. To this end, a test set-up was developed at the ONERA S3Ch wind tunnel. The nacelle models represent a turbofan by means of two compressed air jets. The scale is 1/18.5. The nacelles are fixed on a thrust balance measuring afterbody thrust and discharge coefficients. The wing is located between the sidewalls of the test section. Pressures are measured through 456 holes located on 8 airfoils. Drag coefficient of the wing is obtained by wake survey. The following parameters can vary (1) wing/nacelle position; (2) upstream Mach number (from 0.3 to 0.8); (3) jet pressure ratio; (4) with/without pylon and (5) type of nacelle. Wing nacelle interference can be studied by means of total thrust drag analysis as a functon of the various parameters. The test set-up is described and examples of results are presented.
    Keywords: AERODYNAMICS
    Type: NASA-TM-76606 , May 05, 1980 - May 07, 1980; Munich; Germany
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  • 222
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    Experimental investigation of a transonic potential flow around a symmetric airfoil (1981)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: Experimental flow investigations on smooth airfoils were done using numerical solutions for transonic airfoil streaming with shockless supersonic range. The experimental flow reproduced essential sections of the theoretically computed frictionless solution. Agreement is better in the expansion part of the of the flow than in the compression part. The flow was nearly stationary in the entire velocity range investigated.
    Keywords: AERODYNAMICS
    Type: NASA-TM-76676 , REPT-10/1971
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  • 223
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    Flow and Acoustic Properties of Low Reynolds Number Underexpanded Supersonic Jets (1981)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: Jet noise on underexpanded supersonic jets are studied with emphasis on determining the role played by large scale organized flow fluctuations in the flow and acoustic processes. The experimental conditions of the study were chosen as low Reynolds number (Re=8,000) Mach 1.4 and 2.1, and moderate Reynolds number (Re=68,000) Mach 1.6 underexpanded supersonic jets exhausting from convergent nozzles. At these chosen conditions, detailed experimental measurements were performed to improve the understanding of the flow and acoustic properties of underexpanded supersonic jets.
    Keywords: AERODYNAMICS
    Type: NASA-CR-169257 , NAS 1.26:169257
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  • 224
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    PAN AIR: A computer program for predicting subsonic or supersonic linear potential flows about arbitrary configurations using a higher order panel method. Volume 3: Case manual (version 1.0) (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Numerous applications of the PAN AIR computer program system are presented. PAN AIR is user-oriented tool for analyzing and/or designing aerodynamic configurations in subsonic or supersonic flow using a technique generally referred to as a higher order panel method. Problems solved include simple wings in subsonic and supersonic flow, a wing-body in supersonic flow, wing with deflected flap in subsonic flow, design of two-dimensional and three-dimensional wings, axisymmetric nacelle in supersonic flow, and wing-canard-tail-nacelle-fuselage combination in supersonic flow.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3253 , NAS 1.26:3253
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  • 225
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    Some features of unsteady separating turbulent boundary layers (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The physical features of steady and unsteady separating turbulent boundary layers are discussed with reference to wind-tunnel data obtained at a Reynolds number of 5.1 x 10 to the 6th and a reduced frequency of 0.55. It is shown that a moderate-amplitude (R less than 0.3) oscillating turbulent boundary layer has a mean flow structure that is close to that of a steady free-stream turbulent boundary layer. Well upstream of the separation, unexpected phase shifts of the velocity and turbulence oscillations occur near the wall between the viscous sublayer and the semilogarithmic region. Significant phase variations between the velocity and turbulence also exist in the detached and back flows downstream. Large amplitude oscillations are shown to have a substantial effect on the flow structure.
    Keywords: AERODYNAMICS
    Type: Unsteady turbulent shear flows; Proceedings of the Symposium; May 05, 1981 - May 08, 1981; Toulouse; France
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  • 226
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    PAN AIR: A computer program for predicting subsonic or supersonic linear potential flows about arbitrary configurations using a higher order panel method. Volume 4: Maintenance document (version 1.1) (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Maintenance Document is a guide to the PAN AIR software system, a system which computes the subsonic or supersonic linear potential flow about a body of nearly arbitrary shape, using a higher order panel method. The document describes the over-all system and each program module of the system. Sufficient detail is given for program maintenance, updating and modification. It is assumed that the reader is familiar with programming and CDC (Control Data Corporation) computer systems. The PAN AIR system was written in FORTRAN 4 language except for a few COMPASS language subroutines which exist in the PAN AIR library. Structured programming techniques were used to provide code documentation and maintainability. The operating systems accommodated are NOS 1.2, NOS/BE and SCOPE 2.1.3 on the CDC 6600, 7600 and Cyber 175 computing systems. The system is comprised of a data management system, a program library, an execution control module and nine separate FORTRAN technical modules. Each module calculates part of the posed PAN AIR problem. The data base manager is used to communicate between modules and within modules. The technical modules must be run in a prescribed fashion for each PAN AIR problem. In order to ease the problem of supplying the many JCL cards required to execute the modules, a separate module called MEC (Module Execution Control) was created to automatically supply most of the JCL cards. In addition to the MEC generated JCL, there is an additional set of user supplied JCL cards to initiate the JCL sequence stored on the system.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3254 , NAS 1.26:3254 , D180-24910-4
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  • 227
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    Computer program documentation for a subcritical wing design code using higher order far-field drag minimization (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A subsonic, linearized aerodynamic theory, wing design program for one or two planforms was developed which uses a vortex lattice near field model and a higher order panel method in the far field. The theoretical development of the wake model and its implementation in the vortex lattice design code are summarized and sample results are given. Detailed program usage instructions, sample input and output data, and a program listing are presented in the Appendixes. The far field wake model assumes a wake vortex sheet whose strength varies piecewise linearly in the spanwise direction. From this model analytical expressions for lift coefficient, induced drag coefficient, pitching moment coefficient, and bending moment coefficient were developed. From these relationships a direct optimization scheme is used to determine the optimum wake vorticity distribution for minimum induced drag, subject to constraints on lift, and pitching or bending moment. Integration spanwise yields the bound circulation, which is interpolated in the near field vortex lattice to obtain the design camber surface(s).
    Keywords: AERODYNAMICS
    Type: NASA-CR-3457 , NAS 1.26:3457
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    Viscous-inviscid interaction method including wake effects for three-dimensional wing-body configurations (1981)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A viscous-inviscid interaction method has been developed by using a three-dimensional integral boundary-layer method which produces results in good agreement with a finite-difference method in a fraction of the computer time. The integral method is stable and robust and incorporates a model for computation in a small region of streamwise separation. A locally two-dimensional wake model, accounting for thickness and curvature effects, is also included in the interaction procedure. Computation time spent in converging an interacted result is, many times, only slightly greater than that required to converge an inviscid calculation. Results are shown from the interaction method, run at experimental angle of attack, Reynolds number, and Mach number, on a wing-body test case for which viscous effects are large. Agreement with experiment is good; in particular, the present wake model improves prediction of the spanwise lift distribution and lower surface cove pressure.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1910 , L-14053 , NAS 1.60:1910 , AIAA PAPER 81-1266 , AIAA 14th Fluid and Plasma Dyn. Conf.; Jun 22, 1981 - Jun 24, 1981; Palo Alto, CA; United States
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  • 229
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    A turbulent flow Navier-Stokes analysis for an airfoil oscillating in pitch (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A time-dependent compressible turbulent Navier-Stokes analysis is applied to the oscillating airfoil flow field problem. The turbulence model is based upon a turbulence energy equation. Results obtained for an airfoil oscillating in pitch are compared to data.
    Keywords: AERODYNAMICS
    Type: Unsteady turbulent shear flows; Proceedings of the Symposium; May 05, 1981 - May 08, 1981; Toulouse; France
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  • 230
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    Current developments lighter than air systems (1981)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: Lighter than air aircraft (LTA) developments and research in the United States and other countries are reviewed. The emphasis in the U.S. is on VTOL airships capable of heavy lift, and on long endurance types for coastal maritime patrol. Design concepts include hybrids which combine heavier than air and LTA components and characteristics. Research programs are concentrated on aerodynamics, flight dynamics, and control of hybrid types.
    Keywords: AERODYNAMICS
    Type: NASA-TM-84744 , NAS 1.15:84744
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  • 231
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    Experimental investigation of the flow on the suction side of a thin Delta wing (1981)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: Surface oil flow patterns were photographed and pressure distribution measurements were carried out on a sharp edged delta wing of aspect ratio lambda = 1.0 in order to determine the influence of Reynolds number and of vortex breakdown on the flow on the suction side of the wing. The formation of the secondary vortex occurs due to separation of a laminar boundary layer in the front part of the wing and due to separation of a turbulent boundary layer in the rear part of the wing. In the case of turbulent separation, the secondary separation line is closer to the wing leading edge than in the laminar case. The position of the transition depends on the Reynolds number and on the angle of incidence. The breakdown of a vortex above the wing leads to a kink in the secondary separation line.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75897
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  • 232
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    Separation behavior of boundary layers on three-dimensional wings (1981)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: An inverse boundary layer procedure for calculating separated, turbulent boundary layers at infinitely long, crabbing wing was developed. The procedure was developed for calculating three dimensional, incompressible turbulent boundary layers was expanded to adiabatic, compressible flows. Example calculations with transsonic wings were made including viscose effects. In this case an approximated calculation method described for areas of separated, turbulent boundary layers, permitting calculation of this displacement thickness. The laminar boundary layer development was calculated with inclined ellipsoids.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75877
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  • 233
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    Determination of rotor wake induced empennage airloads (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A computer program has been developed that predicts the unsteady aerodynamic forces that impinge on the empennage surface due to its interactions with the main rotor wake. The program was utilized to determine the vibration airloads acting on the Black Hawk horizontal stabilizer and on the CH-53A stabilizer under high speed forward flight conditions. The results demonstrate that it is possible to compute the high frequency empennage vibration airloads efficiently by utilizing suitable analysis techniques; a CH-53A case required only 1.3 minutes of computer time. Numerical problems associated with the unsteady Kutta condition have been minimized. Even though the analysis is of transient nature, the results for harmonic cases show a very fast convergence to periodicity. In general, good correlation was shown between the predicted vibratory airloads and the measured stabilizer airloads for a CH-53A helicopter operating at high speed flight conditions.
    Keywords: AERODYNAMICS
    Type: AHS PREPRINT 81-26 , Northeast Region National Specialists'' Meeting on Helicopter Vibration: Technology for the Jet Smooth Ride; Nov 02, 1981 - Nov 04, 1981; Hartford, CT
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  • 234
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    Thrust-induced effects on low-speed aerodynamics of fighter aircraft (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The design and technology requirements for STOL fighter aircraft as defined in NASA studies are reviewed. The research has concentrated on advanced high-lift systems using mechanical flaps, methods of obtaining longitudinal trim during the use of thrust vectoring, and thrust reversal to shorten ground roll distances. Several early configurations are described, and investigations of the effect of thrust reversal on the low-speed aerodynamics of the F-15 are detailed. Although the NASA design was a wing-canard configuration, similarities in a Grumman baseline STOL aircraft allowed incorporation of the Grumman nacelle, primary nozzles, spanwise blowing nozzles, and trailing-edge flap systems.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-2612 , V/STOL Conference; Dec 07, 1981 - Dec 09, 1981; Palo Alto, CA
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  • 235
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    A summary of jet-impingement studies at McDonnell Douglas Research Laboratories (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: It has been the primary objective of the considered studies to determine and describe, through calculation, measurement, and visualization of the flowfields, the basic character of isolated and interacting impinging jets. The secondary objective has been to provide computed and experimental flow properties which can be used in the development and verification of empirically based prediction methodologies for complete aircraft configurations. The studies have resulted in the solution of the Reynolds-averaged Navier-Stokes and Jones-Launder turbulence model equations for two- and three-dimensional configurations and in the acquisition of an extensive data base and flow-visualization photographs for these configurations.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-2613 , V/STOL Conference; Dec 07, 1981 - Dec 09, 1981; Palo Alto, CA
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  • 236
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    Research analysis of Space Shuttle Orbiter entry aerothermodynamic flight data at the NASA Langley Research Center (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The methods used to analyze the aerothermodynamic data gathered from the Shuttle protoflights are reviewed. Trajectory and atmospheric reconstruction allow an accurate definition of the freestream environment through which the Shuttle has flown. The reconstructions, combined with aerodynamic coefficient and convective heating rate determinations, provide predictive capability for comparison with future flights. Data are acquired by operational instrumentation (12,000 parameters), development flight instrumentation (4500 measurements), and Orbiter experiments instrumentation; tracking and meteorological data are also included in the analyses. The aerothermodynamic and aerodynamic technology base for large, winged, lifting body entry vehicles is being expanded by the analysis efforts. Sensor locations on the Shuttle and data management techniques are described.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-2429 , Flight Testing Conference; Nov 11, 1981 - Nov 13, 1981; Las Vegas, NV
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  • 237
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    Interaction of upstream flow distortions with high Mach number cascades (1981)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Features of the interaction of flow distortions, such as gusts and wakes with blade rows of advance type fans and compressors having high tip Mach numbers are modeled. A typical disturbance was assumed to have harmonic time dependence and was described, at a far upstream location, in three orthogonal spatial coordinates by a double Fourier series. It was convected at supersonic relative to a linear cascade described as an unrolled annulus. Conditions were selected so that the component of this velocity parallel to the axis of the turbomachine was subsonic, permitting interaction between blades through the upstream as well as downstream flow media. A strong, nearly normal shock was considered in the blade passages which was allowed curvature and displacement. The flows before and after the shock were linearized relative to uniform mean velocities in their respective regions. Solution of the descriptive equations was by adaption of the Wiener-Hopf technique, enabling a determination of distortion patterns through and downstream of the cascade as well as pressure distributions on the blade and surfaces. Details of interaction of the disturbance with the in-passage shock were discussed. Infuences of amplitude, wave length, and phase of the disturbance on lifts and moments of cascade configurations are presented. Numerical results are clarified by reference to an especially orderly pattern of upstream vertical motion in relation to the cascade parameters.
    Keywords: AERODYNAMICS
    Type: NASA-TM-82759 , E-1078 , Ann. Gas Turbine Conf.,; Apr 18, 1982 - Apr 22, 1982; London
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  • 238
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    Low speed testing of the inlets designed for a tamden-fan V/STOL nacelle (1981)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: An approximately 0.25 scale model of a tandem fan nacelle, designed for a subsonic V/STOL aircraft, was tested in a Lewis wind tunnel. Model variables included long and short aft inlet cowls and the addition of exterior strakes to the short inlet cowl. Inlet pressure recoveries and distortion were measured at pitch angles to 40 deg and at combinations of pitch and yaw to 30 deg. Airspeeds covered a range to 135 knots (69 m/sec). The short aft inlet with added strakes had the best aerodynamic performance and is considered suitable for the intended V/STOL application.
    Keywords: AERODYNAMICS
    Type: NASA-TM-82728 , E-1031 , AIAA PAPER 81-2627 , V/STOL Conf.; Dec 07, 1981 - Dec 09, 1981; Palo Alto, CA; United States
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  • 239
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    Computation of high Reynolds number internal/external flows (1981)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A general, user oriented computer program, called VNAP2, was developed to calculate high Reynolds number, internal/ external flows. The VNAP2 program solves the two dimensional, time dependent Navier-Stokes equations. The turbulence is modeled with either a mixing-length, a one transport equation, or a two transport equation model. Interior grid points are computed using the explicit MacCormack Scheme with special procedures to speed up the calculation in the fine grid. All boundary conditions are calculated using a reference plane characteristic scheme with the viscous terms treated as source terms. Several internal, external, and internal/external flow calculations are presented.
    Keywords: AERODYNAMICS
    Type: NASA-TM-84049 , DE81-025343 , LA-UR-81-1882 , CONF-810664-2 , AIAA Computational Fluid Dyn. Conf.; Jun 22, 1981 - Jun 23, 1981; Palo Alto, CA; United States
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  • 240
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    A continuous-vorticity panel method for lifting surfaces (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A continuous-vorticity panel method is developed and utilized to predict the steady aerodynamic loads on lifting surfaces having sharp-edge separation. Triangular panels with linearly varying vorticity are used. The velocity field generated by an individual element is obtained in closed form. An optimization scheme is constructed for finding the vorticity at the nodes of the elements. The method is not restricted by aspect ratios, angles of attack, planforms, or camber. Rectangular and delta wings are presented as numerical examples. The numerical results are in good agreement with the experimental data for incompressible flows.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1895 , Atmospheric Flight Mechanics Conference; Aug 19, 1981 - Aug 21, 1981; Albuquerque, NM
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  • 241
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    Heat transfer on a flat plate in continuum to rarefied hypersonic flows at Mach numbers of 19.2 and 25.4 (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Local heat transfer rates were measured on a flat steel plate (10 in. wide and 16 in. long) with sharp and blunt leading edges (0.001 and 0.010 in.) in the transition from the strong interaction boundary layer regime with no slip at the surface to the free molecule regime. The tests were conducted in a combustion driven hypersonic shock tunnel, with the nominal free stream Mach numbers of 19.2 and 25.4, and a reflected stagnation temperature of approximately 2340 R. The twelve heat transfer gages were made of platinum sputtered on a Pyrex backing to a thickness of approximately 350 A, insulated by a silicone dioxide film. For both Mach numbers the heat transfer data agreed reasonably well with the strong interaction prediction of Li and Nagamatsu (1953, 1955) for unit Reynolds numbers greater than approximately 100,000 and leading edge Knudsen numbers less than approximately 4. At lower density conditions the rarefied flow effects began to dominate the flow phenomena near the leading edge region of the sharp flat plate. A systematic reduction in the heat transfer rate close to the leading edge was observed for both Mach number tests as the leading edge density was reduced and the mean free path was increased.
    Keywords: AERODYNAMICS
    Type: DGLR PAPER 81-009 , Deutsche Gesellschaft fuer Luft- und Raumfahrt, Jahrestagung; May 11, 1981 - May 14, 1981; Aachen; Germany
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  • 242
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    Measurements of the boundary layer and near wake of a supercritical airfoil at cruise conditions (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The flow behavior within the upper-surface boundary layer and near wake of a supercritical airfoil operating at cruise conditions is discussed. Experimental results obtained from wind-tunnel tests are presented which provide a more detailed description of the flow in these regions than was previously available. Mean streamwise velocity profiles measured by pitot-pressure-probe and laser-velocimeter techniques were found to be in excellent agreement. Other mean-flow properties obtained by the laser-velocimeter technique were the local flow angles in the viscous layers and the static pressures at the edges of the boundary layer and wake. The data set also includes measurements of the turbulence intensity and turbulent Reynolds-stress distributions as obtained by the laser-velocimeter technique. To assess the effects of the shock wave, a less extensive set of measurements was realized at a subcritical test condition. The two test conditions (Mach number at free-stream conditions = 0.72, airfoil section lift coefficient = 0.76 and Mach number of free-stream conditions = 0.5, airfoil section lift coefficient = 0.75) provide a good test for state-of-the-art prediction methods because the upper-surface-boundary layer is separated just upstream of the trailing edge in both cases.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1242 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 243
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    A survey of aftbody flow prediction methods (1981)
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    Publication Date: 2019-07-13
    Description: A survey of computational methods used in the calculation of nozzle aftbody flows is presented. One class of methods reviewed are those which patch together solutions for the inviscid, boundary layer, and plume flow regions. The second class of methods reviewed are those which computationally solve the Navier Stokes equations over nozzle aftbodies with jet exhaust flow. Computed results from the methods are compared with experiment. Advantages and disadvantages of the various methods are discussed along with opportunities for further development of these methods.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1694 , Aircraft Systems and Technology Conference; Aug 11, 1981 - Aug 13, 1981; Dayton, OH
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  • 244
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    Self-induced wing rock of slender delta wings (1981)
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    Publication Date: 2019-07-13
    Description: As part of a research program aimed at exploring basic mechanisms that cause wing rock in combat aircraft, an investigation was conducted to study the aerodynamic factors which cause the low-speed wing rock exhibited by slender delta wings. A flat-plate delta wing with 80 deg leading-edge sweep was subjected to conventional static-force tests and dynamic wind-tunnel experiments which included forced-oscillation, rotary, and free-to-roll tests. In addition, visualization of the flow phenomena involved was obtained by observing tuft patterns and using a helium-bubble technique. This paper summarizes the results of this study. Fundamental information is presented on the aerodynamic mechanisms that cause the wing rock and the problem of mathematically modeling the aerodynamics and motions is discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1883 , Atmospheric Flight Mechanics Conference; Aug 19, 1981 - Aug 21, 1981; Albuquerque, NM
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  • 245
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    Full-scale wind-tunnel study of wing-fuselage interaction and comparison with paneling method (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Full-scale wind-tunnel tests, conducted to determine the effects of three different airfoil sections on the aft-fuselage drag of a low-wing aircraft, are described. The measurements indicate a maximum difference in aft fuselage drag between the three airfoils of about 0.002. Measured changes in the locations of the fuselage pressure contours with airfoil section correlated well with the changes predicted by a three dimensional paneling code. A criterion, based on the inviscid computer code, is then proposed as an indicator for possible adverse viscous interactions at the wing-fuselage juncture.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1666 , Aircraft Systems and Technology Conference; Aug 11, 1981 - Aug 13, 1981; Dayton, OH
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  • 246
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    A vortex-lattice method for calculating lifting-surface interference (1981)
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    Publication Date: 2019-07-13
    Description: The interference effect of closely coupled lifting surfaces was investigated. A nonsteady vortex-lattice method was applied to calculate the steady-state and nonsteady lift characteristics of configurations having interference effects. The configurations consist of low-aspect-ratio delta wings, at low and high angles of attack. Leading-edge separation and wake roll-up are simulated by a time-dependent wake-shedding procedure. For steady-state flow conditions, this numerical procedure saves a considerable amount of computer time, compared with iterative methods, and yields the same results. A better understanding of the interference effect can be gained by using the method to study the transient behavior. The nonsteady approach also offers the capability of calculating various nonsteady motions, as is demonstrated in the calculation of the longitudinal damping.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1662 , Aircraft Systems and Technology Conference; Aug 11, 1981 - Aug 13, 1981; Dayton, OH
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  • 247
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    The influence of leading-edge thrust on twisted and cambered wing design for supersonic cruise (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A study of leading-edge thrust phenomena at supersonic speeds has shown that although these forces are not large, they can be a significant factor in the design of wings for supersonic cruise. It is seen that the rather severe twisted and cambered wing surfaces resulting from the application of present design methods, which ignore leading-edge thrust, can be replaced by more moderate surfaces with little or no loss in aerodynamic efficiency if realistic possibilities for the attainment of some fraction of the theoretical thrust are taken into account.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1656 , Aircraft Systems and Technology Conference; Aug 11, 1981 - Aug 13, 1981; Dayton, OH
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  • 248
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    Summary of high-lift and control surface research on NASA general aviation airfoils (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Summary findings and bibliographical information are presented for airfoil and airfoil-related research conducted at Wichita State University during the past decade. Topics include flap, aileron, and spoiler design data for new airfoils, extensive flow measurements, modifications to older airfoils, new symmetrical sections and contributions to analytical methods for cases with partial separation.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 810629 , Business Aircraft Meeting and Exposition; Apr 07, 1981 - Apr 10, 1981; Wichita, KS
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  • 249
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    Aerodynamic design data for a cruise-matched high performance single-engine airplane (1981)
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    Publication Date: 2019-07-13
    Description: Design data are presented for a class of high-performance single-engine business airplanes. The design objectives include a cruise speed of 300 knots, a cruise altitude of 10,700 m (35,000 ft), a cruise payload of six passengers (including crew and baggage), and a no-reserves cruise range of 1300 n.mi. Two unconventional aerodynamic technologies were evaluated: the individual and combined effects of cruise-matched wing loading and of a natural laminar flow airfoil were analyzed. The trade-off data presented illustrate the ranges of wing geometries, propulsion requirements, airplane weights, and aerodynamic characteristics which are necessary to meet the design objectives. Very large design and performance improvements resulted from use of the aerodynamic technologies evaluated. It is shown that the potential exists for achieving more than 200-percent greater fuel efficiency than is achieved by current airplanes capable of similar cruise speeds, payloads, and ranges.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 810625 , Business Aircraft Meeting and Exposition; Apr 07, 1981 - Apr 10, 1981; Wichita, KS
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  • 250
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    Noise and performance of general aviation aircraft - A review of the MIT study (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The primary objective of the study was to explore the possibility of reducing noise from a general-aviation-type propeller without altering significantly its aerodynamic performance or the engine characteristics. Our study of this possibility involved aerodynamic and acoustic theory, design, construction, and wind tunnel testing of model propellers, design and manufacture of full-scale propellers, and, finally, flight tests. One propeller exhibited an overall measured reduction of 4.8 dBA during a flight test. This reduction was achieved with minimal changes in performance.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 810586 , Business Aircraft Meeting and Exposition; Apr 07, 1981 - Apr 10, 1981; Wichita, KS
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  • 251
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    Wind-tunnel measurements of wing-canard interference and a comparison with various theories (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Wind-tunnel tests and analyses of the aerodynamics of wing-canard combinations for low speed applications are presented. Systematic tests are conducted in a 7 x 10 wind tunnel to explore various combinations of wing-canard vertical and horizontal positioning. The goals of the tests are (1) to investigate potential improved stalling characteristics over conventional tail-aft configurations, (2) to investigate the existence of a lift coefficient advantage, and (3) to determine induced drag levels. The measurements obtained are compared with calculations made using the Prandtl-Munk theory, and with a vortex-lattice panel code. Results indicate that the panel code gives excellent results for lift and induced drag at moderate lift coefficient, whereas Prandtl-Munk theory gives conservative results for induced drag. The application is a light transport aircraft used for short-haul operations.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 810575 , Business Aircraft Meeting and Exposition; Apr 07, 1981 - Apr 10, 1981; Wichita, KS
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  • 252
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    Transonic wing design using potential-flow codes - Successes and failures (1981)
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    Publication Date: 2019-07-13
    Description: The state-of-the-art of transonic wing design by use of computer codes based on the potential flow-theory is presented. The capabilities and limitations of these codes are exemplified by several experiment-theory correlations, including an assessment of pressure distribution from isolated wing and wing-body codes. Computer codes using both conservative and nonconservative differencing schemes were used, and the effects of boundary-layer corrections were considered. Results showed that calculations from a full potential, isolated code correlate well with data from an isolated wing test, but may give poor predictions of the aerodynamic characteristics of some wing-body configurations. Boundary-layer correlations were found to have only moderate effects on experiment-theory correlation. Aeroelastic effects were considered important for high aspect ratio wings of low to moderate thickness, and viscous effects were minimal for typical cruise conditions, even for Reynold's numbers as low as two million. The effect of wind-tunnel walls on experiment-theory correlations remained inconclusive. A wing-body code was used to calculate the flow field about a wing-body configuration with body-mounted engines, typical of the transonic Biz-Jet aircraft.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 810565 , Business Aircraft Meeting and Exposition; Apr 07, 1981 - Apr 10, 1981; Wichita, KS
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    Inlet design technology development - Supersonic cruise research (1981)
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    Publication Date: 2019-07-13
    Description: An inlet technology development program for future supersonic cruise aircraft is in progress. Areas being emphasized are inlet aerodynamic and control system design requirements for efficient and reliable operation. Off-design conditions, such as angle of incidence, starting, and noise abatement are major considerations. Flow analysis procedures are being developed to predict the internal inviscid and viscous flows in axisymmtric supersonic inlets for these operating conditions. Also under development are control systems that will have significant interfaces with the engine control system, the flight control system, and the airframe avionics system. The analytical methods are being supported and validated with representative experiments.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1598 , Joint Propulsion Conference; Jul 27, 1981 - Jul 29, 1981; Colorado Springs, CO; US
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    Laser-velocimeter flow-field measurements of an advanced turboprop (1981)
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    Publication Date: 2019-07-13
    Description: Non-intrusive measurements of velocity about a spinner-propeller-nacelle configuration at a Mach number of 0.8 have been performed. A laser velocimeter, specifically developed for these measurements in the NASA Lewis 8- by 6-foot Supersonic Wind Tunnel, was used to measure the flow-field of the advanced swept SR-3 propeller. The laser velocimeter uses an argon ion laser and a 2-color optics system to allow simultaneous measurements of 2-components of velocity. The axisymmetric nature of the propeller-nacelle flow-field permits two separate 2-dimensional measurements to be combined into 3-dimensional velocity data. Presented are data ahead of and behind the propeller blades and also a limited set in between the blades. Aspects of the observed flow-field such as the tip vortex are discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1568 , Joint Propulsion Conference; Jul 27, 1981 - Jul 29, 1981; Colorado Springs, CO; US
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  • 255
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    Factors influencing the predicted performance of advanced propeller designs (1981)
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    Publication Date: 2019-07-13
    Description: The assumptions on which conventional propeller aerodynamic performance analyses are based can be seriously violated when advanced high speed propellers are analyzed. Studies have been performed using a lifting line representation for the propeller to determine the sensitivity of predicted propeller performance to various assumptions in the analysis. Items which have been studied include the method of determining blade section lift and the effects of blade section drag, camber and blade sweep. The effects of nonuniform flow into the propeller and compressibility have also been studied. Comparisons of analytical and experimental results are presented to demonstrate the overall validity of the results.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1564 , Joint Propulsion Conference; Jul 27, 1981 - Jul 29, 1981; Colorado Springs, CO; US
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  • 256
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    Zero-length inlets for subsonic V/STOL aircraft (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Zero-length inlet performance and associated fan blade stresses were determined during model tests in the NASA-LeRC 9-by 15-foot low-speed wind tunnel. The inlet models, which were installed on a 20-inch diameter fan unit, had different inlet lip contraction ratios as well as unslotted, slotted, and double slotted inlet lips. The inlet angle-of-attack boundaries for onset of flow separation were identified and compared to the operating requirements of several generically different subsonic V/STOL aircraft. The zero-length inlets, especially those with slotted lips, were able to satisfy these requirements without compromising the maximum cowl forebody radius. As an aid to the inlet design process, a unique relationship was established between the maximum surface Mach number associated with the separation boundary and the maximum-to-throat surface velocity ratio.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1396 , Joint Propulsion Conference; Jul 27, 1981 - Jul 29, 1981; Colorado Springs, CO; US
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  • 257
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    Some aspects of calculating flows about three-dimensional subsonic inlets (1981)
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    Publication Date: 2019-07-13
    Description: As a consequence of the growing interest in the development of V/STOL aircraft technology, efforts are being made to create new designs for a propulsion system which can be operated over a wide range of flight speeds, incidence angles, and throttle settings. In connection with these efforts, various inlet configurations have been proposed. The high experimental costs incurred in the study of various inlet geometries, led to the employment of a computational method for the investigation of inlets. Attention is given to the computer program, paneling and surface static pressure, surface flow pattern, and the inlet flow field. The reported investigation demonstrates that useful information for initial screenings may be obtained from potential flow calculations.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1361 , Joint Propulsion Conference; Jul 27, 1981 - Jul 29, 1981; Colorado Springs, CO; US
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  • 258
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    A numerical simulation of two-dimensional inlet flow fields (1981)
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    Publication Date: 2019-07-13
    Description: Inlet flow fields for airbreathing missiles are calculated by the adaptation of a two-dimensional computational method developed for the flow around airfoils. A supersonic free stream is assumed to allow the forebody calculation to be uncoupled from the inlet calculation. The inlet calculation employs an implicit, time-marching finite-difference procedure to solve the thin-layer Navier-Stokes equations formulated in body-fitted coordinates. Because the method can be used for a flow field with both subsonic and supersonic regions, it is applicable to subcritical as well as supercritical inlet operation.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-0187 , Aerospace Sciences Meeting; Jan 12, 1981 - Jan 15, 1981; St. Louis, MO
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  • 259
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    Effects of rotation and blade incidence on the properties of turbomachinery rotor wake (1981)
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    Publication Date: 2019-07-13
    Description: An experimental investigation of the effects of the speed of rotation on a turbomachinery rotor blade wake was conducted using a fan rotor in incompressible flow. Measurements were made at two different rotational speeds (1753 and 1010 rpm) but keeping the same blade loading. This was achieved by maintaining the same incidence angle to the rotor blades in both sets of measurements. The blade incidence angle was also varied to discern the effect of blade loading. A tri-axial hot wire probe mounted in a stationary frame of reference was used for the measurements made at several radial and axial stations in the near- and far-wake regions. The three dimensional mean velocity and turbulence profiles, the wake defect, wake decay rate, turbulence intensities and turbulence stresses are appreciably altered when the speed of rotation and the blade loading are changed. The wake defect is substantially reduced and the radial velocity increased when the rotational speed is increased.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-0054 , Aerospace Sciences Meeting; Jan 12, 1981 - Jan 15, 1981; St. Louis, MO
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  • 260
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    A survey of heating and turbulent boundary layer characteristics of several hypersonic research aircraft configurations (1981)
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    Publication Date: 2019-07-13
    Description: Four of the configurations investigated during a proposed NASA-Langley hypersonic research aircraft program were selected for phase-change-paint heat-transfer testing and forebody boundary layer pitot surveys. In anticipation of future hypersonic aircraft, both published and unpublished data and results are reviewed and presented with the purpose of providing a synoptic heat-transfer data base from the research effort. Engineering heat-transfer predictions are compared with experimental data on both a global and a local basis. The global predictions are shown to be sufficient for purposes of configuration development, and even the local predictions can be adequate when interpreted in light of the proper flow field. In that regard, cross flow in the forebody boundary layers was examined for significant heating and aerodynamic effect on the scramjet engines. A design philosophy which evolved from the research airplane effort is used to design a forebody shape that produces thin, uniform, forebody boundary layers on a hypersonic airbreathing missile. Finally, heating/boundary layer phenomena which are not predictable with state-of-the-art knowledge and techniques are shown and discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1145 , Thermophysics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 261
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    The effect of modeled turbulence on a hypersonic shock layer with massive ablation injection (1981)
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    Publication Date: 2019-07-13
    Description: For the first time, candidate turbulence models are analyzed for shock-layer conditions as severe as those of a Jovian entry. The various models investigated are two standard models developed primarily by Cebeci (1970) and Kendall (1972), and two modifications of the standard models developed primarily by Baldwin and Lomax (1978) and by Nicolet (1979). The analysis is conducted within the context of a new, viscous shock-layer flow-field code, to properly isolate differences in performance among the various models. This code retains all terms in the Navier-Stokes equations necessary to describe the unique flow events, and incorporates computational features that greatly facilitate the analysis of such events. The relative superiority of the turbulence models cannot be determined from this study alone; however, insight is provided into the relative severity of the various models. In addition, attention is focused on an important research area for experimental and theoretical investigation to develop realistic turbulence models.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1071 , Thermophysics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 262
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    Measurement of recovery temperature on an airfoil in the Langley 0.3-m transonic cryogenic tunnel (1981)
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    Publication Date: 2019-07-13
    Description: Experimental measurements of recovery temperature were made on an airfoil in the Langley 0.3-m Transonic Cryogenic Tunnel at Mach numbers of 0.60 and 0.84 over a Reynolds number per meter range from about 15,000,000 to about 335,000,000. The measured recovery temperatures were considerably below those associated with ideal-gas ambient temperature wind tunnels. This difference was accentuated as the stagnation pressure increased and the total temperature decreased. A boundary-layer code modified for use with cryogenic nitrogen adequately predicted the measured adiabatic wall temperature at all conditions. A quantitative, on-line assessment of the nonadiabatic condition of a model can be made during the operation of a cryogenic wind tunnel by using a correlation for the adiabatic wall temperature which is only a function of total temperature, total pressure, and local Mach number on the model.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1062 , Thermophysics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 263
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    An empirical method for computing leeside centerline heating on the Space Shuttle Orbiter (1981)
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    Publication Date: 2019-07-13
    Description: An empirical method is presented for computing top centerline heating on the Space Shuttle Orbiter at simulated reentry conditions. It is shown that the Shuttle's top centerline can be thought of as being under the influence of a swept cylinder flow field. The effective geometry of the flow field, as well as top centerline heating, are directly related to oil-flow patterns on the upper surface of the fuselage. An empirical turbulent swept cylinder heating method was developed based on these considerations. The method takes into account the effects of the vortex-dominated leeside flow field without actually having to compute the detailed properties of such a complex flow. The heating method closely predicts experimental heat-transfer values on the top centerline of a Shuttle model at Mach numbers of 6 and 10 over a wide range in Reynolds number and angle of attack.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1043 , Thermophysics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 264
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    Approximate heating analysis for the windward-symmetry plane of Shuttle-like bodies at large angle of attack (1981)
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    Publication Date: 2019-07-13
    Description: An engineering method has been developed for computing the windward-symmetry plane convective heat-transfer rates on Shuttle-like vehicles at large angles of attack. The engineering code includes an approximate inviscid flowfield technique, laminar and turbulent heating-rate expressions, an approximation to account for the variable-entropy effects on the surface heating and the concept of an equivalent axisymmetric body to model the windward-ray flowfields of Shuttle-like vehicles at angles of attack from 25 to 45 degrees. The engineering method is validated by comparing computed heating results with corresponding experimental data measured on Shuttle and advanced transportation models over a wide range of flow conditions and angles of attack from 25 to 40 degrees and also with results of existing prediction techniques. The comparisons are in good agreement.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1042 , Thermophysics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 265
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    Nonparallel stability of three-dimensional flows (1981)
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    Publication Date: 2019-07-13
    Description: The linear stability of three-dimensional incompressible, isothermal, nonparallel boundary-layer flows has been investigated. The method of multiple scales is used to derive the partial-differential equations that describe the spatial modulations of the amplitude, phase and wavenumber of a disturbance. Group velocities are used to determine the disturbance growth direction. The envelope method is used to calculate the logarithmic amplitude growth rate N. The theory is applied to the flows over a swept-back tapered wing with boundary-layer suction. Results of such analysis for the X-21 wing are discussed. It is found that the nonparallel effects for this wing is substantial.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1281 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 266
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    Computation of hypersonic viscous flow around three-dimensional bodies at high angles of attack (1981)
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    Publication Date: 2019-07-13
    Description: A parabolized Navier-Stokes code capable of predicting steady viscous supersonic flows with cross-flow separation is applied to three-dimensional arbitrary geometries at high angles of attack. The numerical procedure, which is implicit, noniterative, and of second-order accuracy in the marching direction, has been used to compute complicated flow fields containing a relatively thick sonic layer and regions of strong viscous-inviscid interaction. A consistent and accurate procedure has also been developed to provide the necessary starting data through timewise integration of the equations of motion near the nose-tip region of the body. Numerical results obtained from the present method compare well with experiment for both the surface pressures and heat transfer.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1261 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 267
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    Three-dimensional structures and turbulence closure of the wake developing in a wall shear layer (1981)
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    Publication Date: 2019-07-13
    Description: The turbulent wake interacting with the rotating wall shear layer is investigated analytically and numerically. The turbulent wakes of the rotating blades in a compressor which are interacting with the rotating hub-wall boundary layer are analyzed. A modified version of the closure model of the pressure-strain correlation term in the Reynolds stress transport equation is developed to predict the effect of rotation, which is appreciable for the present flow because the thick hub-wall boundary layer is interacting with the rotor wake. It is noted that the Poisson type equation for the pressure-strain correlation has an extra rotation term when the entire flow field is rotating. This extra rotation term is modeled to accommodate the effect of rotation. In addition, the standard correction for the wall effect is incorporated for the utilized Reynolds stress closure model. The rotation-modified Reynolds stress closure model is used to predict the present flow, and the predictions are compared with the experimental data. The experimental data reveal that the characteristics of the three-dimensional turbulent wake interacting with the wall shear layer are considerably altered by the effects of the wall and the rotation. These features are predicted with good accuracy by the turbulence closure model developed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1269 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 268
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    Flow separation in shear-layer-driven cavities (1981)
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    Publication Date: 2019-07-13
    Description: A study of the shear-layer flow over a range of open-top cavity configurations is reported. Emphasis is placed on the effect that altering the cavity's span length and aspect ratio has on the development of the shear layer. Computational results are obtained using an interactive method which adapts the compressible boundary-layer model for the flow above the cavity and incompressible Navier-Stokes equations within the enclosure. Interaction of this composite model with the outer, inviscid supersonic flow is also considered in one case. The results show that the location of the stagnation points is sensitive primarily to the variation of the span. When the span was fixed and the aspect ratio varied, the shear layer was nearly unaffected except at aspect ratios less than 0.5. Interaction with the outer flow had a smoothing effect on the shape of the dividing streamline but did not significantly affect the location of the stagnation points.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1247 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 269
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    Navier-Stokes solutions for nonaxisymmetric nozzle flows (1981)
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    Publication Date: 2019-07-13
    Description: The compressible Navier-Stokes equations for two-dimensional and three-dimensional flow are solved for nonaxisymmetric nozzle configurations. Both internal flow alone and combined internal and external flow cases are considered. An implicit approximate factorization algorithm is employed to solve the governing equations which are cast in terms of a body-fitted coordinate system. Turbulence closure is accomplished with a composite algebraic model. Two-dimensional results for a wedge plug nozzle flow in the form of surface pressures compare favorably with experimental data. Three-dimensional calculations for two nonaxisymmetric nozzles are also presented and compared with data.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1217 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 270
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    On the structure of turbulent wakes and merging shear layers of multielement airfoils (1981)
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    Publication Date: 2019-07-13
    Description: The structure of the attached turbulent flow in the vicinity of a NACA 4412 airfoil equipped with a single-slotted flap was studied. The airfoil/flap configuration was tested at a Mach number of 0.06 and a Reynolds number of 1.3 x 10 to the 6th in a 7- by 10-Foot Wind Tunnel. Surface-pressure measurements were made on the main airfoil and on the flap. Detailed measurements, obtained using a high-spatial-resolution laser Doppler anemometer, were made of the mean velocity flow field and of the second-order statistical quantities (Reynolds stresses) in the boundary layers, wakes, and merging shear layers. The experimental observations are compared with theoretical predictions of pressure, mean velocity, and Reynolds stress.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1238 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 271
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    A numerical study of two-dimensional shock vortex interaction (1981)
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    Publication Date: 2019-07-13
    Description: The numerical analysis of shock vortex interaction in a two-dimensional channel is discussed in this paper. The Euler equations and the two-step MacCormack scheme are employed in this numerical analysis. The comparison of the numerical results with the theoretical analyses and experimental results in the literature has provided unique insights into the dynamics of the transient interaction process and the needs for further theoretical developments. The results are useful in applications to problems in aeroacoustics and the transient aerodynamics of high performance aircraft.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1205 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 272
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    Computation of simple three-dimensional wing-vortex interaction in transonic flow (1981)
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    Publication Date: 2019-07-13
    Description: An implicit delta form finite-difference algorithm for Euler equations in conservation law form has been used in preliminary calculations of three-dimensional wing-vortex interactions. Both steady and unsteady transonic flow wing-vortex interactions are computed. The computations themselves are meant to guide upcoming wind tunnel experiments of the same flow field. Various modifications to the numerical method that are intended to improve computational efficiency are also described and tested in both two- and three-dimensions.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1206 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 273
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    Computation of high Reynolds number internal/external flows (1981)
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    Publication Date: 2019-07-13
    Description: A general, user oriented computer program, called VNAP2, has been developed to calculate high Reynolds number, internal/external flows. VNAP2 solves the two-dimensional, time-dependent Navier-Stokes equations. The turbulence is modeled with either a mixing-length, a one transport equation, or a two transport equation model. Interior grid points are computed using the explicit MacCormack scheme with special procedures to speed up the calculation in the fine grid. All boundary conditions are calculated using a reference plane characteristic scheme with the viscous terms treated as source terms. Several internal, and internal/external flow calculations are presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1194 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 274
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    The effects of sidewall boundary layers in two-dimensional subsonic and transonic wind tunnels (1981)
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    Publication Date: 2019-07-13
    Description: A transonic similarity rule which accounts for the effects of attached sidewall boundary layers in two-dimensional wind tunnels is presented along with results of an experimental investigation of sidewall boundary-layer effects. The rule appears valid provided the sidewall boundary layer both remains attached in the vicinity of the model and occupies a small enough fraction of the tunnel width to avoid substantial three-dimensional interaction with the model.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1297 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 275
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    PAN AIR - A higher order panel method for predicting subsonic or supersonic linear potential flows about arbitrary configurations (1981)
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    Publication Date: 2019-07-13
    Description: PAN AIR is a computer program for predicting subsonic or supersonic linear potential flow about arbitrary configurations. It uses linear source and quadratic doublet strength distributions. These higher-order distributions have been implemented in a manner that greatly reduces the numerical stability problems that have plagued earlier attempts to make surface paneling methods work successfully for supersonic flow. PAN AIR's problem-solving capability, numerical approach, modeling features, and program architecture are described. Numerical results are presented for a variety of geometries at supersonic Mach numbers.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1255 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 276
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    Viscous-inviscid interaction for transonic wing-body configurations including wake effects (1981)
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    Publication Date: 2019-07-13
    Description: An existing three-dimensional compressible integral boundary-layer method was modified to account for mean dilatation effects, to model transition properly, and to provide better numerical stability near computational boundaries. Results of this method were compared against those from a three-dimensional finite-difference boundary-layer method on a difficult test case. An interaction procedure was developed to couple this integral method with a number of wing-alone and wing-body transonic potential codes to account for viscous effects. A strip wake model, including thickness and curvature effects, was developed and incorporated into this interaction procedure. Results from this procedure were compared against experimental data and results from previous procedures, on test cases where viscous effects were large.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1266 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 277
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    Development of a linear unsteady aerodynamic analysis for finite-deflection subsonic cascades (1981)
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    Publication Date: 2019-07-13
    Description: A linear unsteady potential flow analysis, which accounts for the effects of blade geometry and steady turning, is being developed to predict the aerodynamic response to blade vibrations in the fan, compressor or turbine stages of modern jet engines. In previous work numerical solutions were restricted to cascades of sharp-edged blades aligned with the mean flow. Under the present effort the solution procedure has been extended to treat blades with rounded or blunt edges. As part of this effort an analytical model-problem study has been conducted to clarify the behavior of first-order perturbation solutions in the vicinity of airfoil edges. Further, a numerical approximation using concepts from singular perturbation theory has been developed to resolve the unsteady boundary value problem for cascades of blunt leading-edged blades. Numerical results for NACA 0012 cascades, including detailed results in the vicinity of a blade leading edge, are presented and evaluated.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1290 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 278
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    Numerical simulation of transonic flows in diffusers (1981)
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    Publication Date: 2019-07-13
    Description: Numerical simulations were made of two-dimensional transonic flows in diffusers, including flow separation induced by a shock or adverse pressure gradient. The mass-averaged, time-dependent, compressible Navier-Stokes equations, simplified by the thin-layer approximation, were solved using MacCormack's hybrid method. The eddy-viscosity formulation was described by the Wilcox-Rubesin's two-equation, k-omega model. Detailed comparison of the computed results with measurements showed good agreement in all cases, including one with massive separation induced by a strong shock. The computation correctly predicted the details of a distinct lambda shock pattern, closely duplicating the configuration observed experimentally in spark-schlieren photographs.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1240 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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    Computation of separated flows by a vortex-tracing algorithm (1981)
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    Publication Date: 2019-07-13
    Description: Numerical solutions for two-dimensional, time-dependent, separated flows around bodies are obtained, using a new version of the vortex method. This method provides an efficient representation of flows involving large regions of separation. The modifications incorporated in the new version, which improve its accuracy, versatility, and computing speed, are described. The computer cost is only of the order of the 3/2 power on N, instead of N-squared, for each step with N vortices. Arbitrary shapes can be treated; a conformal mapping is not required. Special attention is paid to the viscous character of the solution and to the accurate computation of the pressure distribution at the body surface. The vortex solution for the outer flow is coupled to an inner solution for the attached part of the boundary layer. Numerical results are presented for several bluff bodies exhibiting dependence on Reynolds number, for stationary airfoils under steady or transient conditions and for oscillating airfoils, including dynamic stalls. These results are compared with other available results, analytical or experimental, and demonstrate the enhanced reliability and accuracy of the improved method.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1246 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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    Some anomalies between wind tunnel and flight transition results (1981)
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    Publication Date: 2019-07-13
    Description: A review of environmental disturbance influence and boundary layer transition measurements on a large collection of reference sharp cone tests in wind tunnels and of recent transonic-supersonic cone flight results have previously demonstrated the dominance of free-stream disturbance level on the transition process from the beginning to end. Variation of the ratio of transition Reynolds number at onset-to-end with Mach number has been shown to be consistently different between flight and wind tunnels. Previous correlations of the end of transition with disturbance level give good results for flight and large number of tunnels, however, anomalies occur for similar correlation based on transition onset. Present cone results with a tunnel sonic throat reduced the disturbance level by an order of magnitude with transition values comparable to flight.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1225 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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    Conservative full-potential calculations for axisymmetric, transonic flow (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A conservative, finite-difference, full-potential relaxation code has been developed to solve transonic flow around axisymmetric or nonlifting, planar, two-dimensional bodies. The program utilizes the artificial compressibility method to provide an upwind bias in supersonic regions. Calculated examples include a wide variety of axisymmetric and planar two-dimensional shapes with various blunt, pointed and open ends in subsonic, transonic, and low supersonic free streams. Comparisons between conservative and nonconservative full-potential calculations show perfect agreement at convergence when the flow is entirely subsonic. Noticeable differences exist, however, between the conservative and nonconservative solutions for transonic flows with shocks.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1204 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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  • 282
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    A method for computation of inviscid three-dimensional flow over blunt bodies having large embedded subsonic regions (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A computational technique for computing the three-dimensional inviscid flow over blunt bodies having large regions of embedded subsonic flow is detailed. Results, which were obtained using the CDC Cyber 203 vector processing computer, are presented for several analytic shapes with some comparison to experimental data. Finally, windward surface pressure computations over the first third of the Space Shuttle vehicle are compared with experimental data for angles of attack between 25 and 45 degrees.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1203 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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    Aerodynamic features of designed strake-wing configurations (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Sixteen analytically and empirically designed strakes have been aerodynamically tested on a common wing-body to determine the longitudinal characteristics of the configurations. These strakes were selected, in general, due to their superior performance in a water-tunnel test. There they exhibited a good correlation between the hypothesized high value of angle of attack for strake vortex breakdown and the high value of leading-edge suction at the strake tip. The lift and pitch data were reasonably well predicted by an extended suction analogy method, and the lift agreement improved with increasing strake area. The strake-vortex-breakdown angle and configuration maximum lift generally increase with increasing strake area and, to some extent, strake tip leading-edge suction value. The best strake configurations all developed about the same maximum area efficiency value despite their differences in size.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1214 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
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    Transonic airfoil calculations using solution-adaptive grids (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A new algorithm for generating solution-adaptive grids (SAG) about airfoil configurations embedded in transonic flow is presented. The present SAG approach uses only the airfoil surface solution to recluster grid points on the airfoil surface, i.e., the reclustering problem is one dimension smaller than the flow-field calculation problem. Special controls automatically built into the elliptic grid generation procedure are then used to obtain grids with suitable interior behavior. This concept of redistributing grid points greatly simplifies the idea of solution-adaptive grids. Numerical results indicate significant improvements in accuracy for SAG grids relative to standard grids using the same number of points.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1010 , Computational Fluid Dynamics Conference; Jun 22, 1981 - Jun 23, 1981; Palo Alto, CA
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    The use of adaptive grids in conjunction with shock capturing methods (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The use of shock capturing finite-difference techniques in computing flow fields containing shocks results in a smeared or oscillatory solution in the vicinity of the shocks. This smearing or oscillatory behavior is due to the discretized form of the governing differential equations used to compute the solution. The discretization error can be reduced by a proper clustering of mesh points in the region of the shock and by using shock aligned grids. This paper uses a simple method that was developed earlier to cluster points near the shocks and serves to introduce a new method of generating a shock aligned mesh. Applications to the one-dimensional inviscid Burgers' equation, supersonic flow over a wedge with the associated straight oblique shock, one- and two-dimensional inviscid flows through an expanding duct and the problem of a straight oblique shock in a uniform supersonic freestream are presented. Significant reduction in the oscillatory behavior of the solution is demonstrated.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1012 , Computational Fluid Dynamics Conference; Jun 22, 1981 - Jun 23, 1981; Palo Alto, CA
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  • 286
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    An implicit marching procedure for the treatment of supersonic flow fields using the conservative full potential equation (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A new aerodynamic prediction technique based on the conservative full potential equation is developed for the treatment of supersonic flow fields. This new technique bridges the gap between simplistic linear theory methods and complex Euler solvers. A novel local density linearization concept and a second order accurate retarded density scheme, both producing the correct artificial viscosity, are introduced in developing an implicit marching scheme for solving the scalar phi. The method produces results that compare well with Euler solvers and requires an order of magnitude less computer time and significantly less computer memory over existing nonlinear codes. The scalar phi formulation can be extended to handle subsonic pockets in the marching direction and also is suitable for developing inverse procedures where the shape corresponding to a prescribed loading is sought.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1004 , Computational Fluid Dynamics Conference; Jun 22, 1981 - Jun 23, 1981; Palo Alto, CA
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    Numerical simulation of steady transonic flow about airfoils (1981)
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    Publication Date: 2019-07-13
    Description: A computer code has been developed that couples a fast transonic full-potential AF2 solver with both an efficient integral boundary-layer method and a viscous wedge approximation of the shock/boundary-layer interaction. The efficiency of the coupled analysis methods and the method of coupling has resulted in a uniquely efficient analysis tool. The airfoil geometry is modified by the displacement thickness before the shock and the displacement thickness plus the viscous wedge thickness after the shock by considering the viscous effects as an equivalent transpiration boundary condition. The flow about conventional and supercritical airfoils under moderately strong shock situations has been calculated. Comparisons with experimental data indicate that this viscous correction method has improved the accuracy of the full-potential analysis. Furthermore, the computer time required to obtain a converged solution has been reduced.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1002 , Computational Fluid Dynamics Conference; Jun 22, 1981 - Jun 23, 1981; Palo Alto, CA
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    Aerodynamic characteristics of a series of airbreathing missile configurations (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The results of an experimental program conducted in order to compile a data base useful in the application of airbreathing propulsion to missiles are presented. The configurations investigated used two-dimensional or axisymmetric twin inlets located at three alternative circumferential positions: 90, 115 and 135 deg to the vertical centerline. The effects of a wing located above the inlets and of various tail configurations were investigated, with a view to longitudinal stability/control and lateral-directional stability characteristics. It is noted that of the three tail configurations tested, the 'X' tail showed (1) the most linear pitch-moment curve, (2) control effectiveness, and (3) positive lateral-directional stability.
    Keywords: AERODYNAMICS
    Type: Symposium on Aeroballistics; May 12, 1981 - May 14, 1981; Carderock, MD
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    Wake vortex alleviation (1981)
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    Publication Date: 2019-07-13
    Description: This paper describes some of the National Aeronautics and Space Administration's (NASA's) recent and current research on aerodynamic techniques for minimizing the aircraft trailing vortex hazard. The potential benefits and operating problems of the more promising concepts are discussed. Recent flight-test results are presented which show that essentially total vortex alleviation can be achieved at a 3 nautical mile separation distance by oscillating the aircraft's lateral-control surfaces. While not operationally practical, these results suggest that it may be possible to minimize the wake hazard by exciting longitudinal instabilities.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-0798 , International Air Transportation Conference; May 26, 1981 - May 28, 1981; Atlantic City, NJ; US
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    Rotor wake mixing effects downstream of a compressor rotor (1981)
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    Publication Date: 2019-07-13
    Description: An experimental study of rotor wake was conducted in the trailing-edge and near-wake regions of a moderately loaded compressor rotor blade using a rotating triaxial hot-wire probe in a rotating frame of reference. The flow-field was surveyed very close to the trailing-edge as well as inside the annulus- and hub-wall boundary layers. The large amount of data acquired during this program has been analyzed to discern the decay effects as well as the spanwise variation of three components of velocity, three components of intensities and three components of shear stresses. The data set also include extensive information on the variation of the flow properties downstream. The other derived quantities include wake momentum thickness and deviation angles at various spanwise and downstream locations. These data are presented and interpreted, with emphasis on the downstream mixing as well as endwall-wake interaction effects.
    Keywords: AERODYNAMICS
    Type: ASME PAPER 81-GT-98 , Gas Turbine Conference and Products Show; Mar 09, 1981 - Mar 12, 1981; Houston, TX
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    A simple model for compressor stall cell propagation (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A simple model for full-span stall cells in axial compressors has been formulated. The sudden changes in velocity across blade rows as the blade passages enter and leave the stall are shown to have important dynamical consequences for the stall flow field. The one empirical constant needed in the analysis is determined using the data of Day (1976, 1978). From this, reasonable predictions of stall cell speed and trends in speed have been obtained for a number of different compressors. From the satisfactory comparison between predicted and measured stall cell speeds, it is tentatively concluded that the model contains the essentials of a correct description of the controlling mechanism of full-span rotating stall.
    Keywords: AERODYNAMICS
    Type: ASME PAPER 81-GT-73 , Gas Turbine Conference and Products Show; Mar 09, 1981 - Mar 12, 1981; Houston, TX
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    Fluid mechanics mechanisms in the stall process of airfoils for helicopters (1981)
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    Publication Date: 2019-07-13
    Description: Phenomena that control the flow during the stall portion of a dynamic stall cycle are analyzed, and their effect on blade motion is outlined. Four mechanisms by which dynamic stall may be initiated are identified: (1) bursting of the separation bubble, (2) flow reversal in the turbulent boundary layer on the airfoil upper surface, (3) shock wave-boundary layer interaction behind the airfoil crest, and (4) acoustic wave propagation below the airfoil. The fluid mechanics that contribute to the identified flow phenomena are summarized, and the usefulness of a model that incorporates the required fluid mechanics mechanisms is discussed.
    Keywords: AERODYNAMICS
    Type: Symposium on Numerical and Physical Aspects of Aerodynamic Flows; Jan 19, 1981 - Jan 21, 1981; Long Beach, CA
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    Laser velocimetry applied to transonic flow past airfoils (1981)
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    Publication Date: 2019-07-13
    Description: Measurements of turbulent Reynolds stresses and mean velocities obtained by laser velocimetry for cases of transonic shock-induced separation are presented. These results are compared with solutions of the Reynolds-averaged time-independent compressible Navier-Stokes equations. Insufficient agreement between predictions and experimental results is attributed to the deficiencies in the models for the turbulence Reynolds stresses.
    Keywords: AERODYNAMICS
    Type: Symposium on Numerical and Physical Aspects of Aerodynamic Flows; Jan 19, 1981 - Jan 21, 1981; Long Beach, CA
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    Investigation of aerodynamic characteristics of wings having vortex flow using different numerical codes (1981)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The aerodynamic characteristics of highly sweptback wings having separation-induced vortex flow were investigated by employing different numerical codes with a view to determining some of the capabilities and limitations of these codes. Flat wings of various configurations-strake wing models, cropped, diamond, arrow and double delta wings, were studied. Cambered and cranked planforms have also been tested. The theoretical results predicted by the codes were compared with the experimental data, wherever possible, and found to agree favorably for most of the configurations investigated. However, large cambered wings could not be successfully modeled by the codes. It appears that the final solution in the free vortex sheet method is affected by the selection of the initial solution. Accumulated span loadings estimated for delta and diamond wings were found to be unusual in comparison with attached flow results in that the slopes of these load curves near the leading edge do not tend to infinity as they do in the case of attached flow.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165706
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    Application of thrusting ejectors to tactical aircraft having vertical lift and short-field capability (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The status of ejector development in terms of application to V/STOL aircraft is reported in three categories: aircraft systems and ejector concepts; ejector performance including prediction techniques and experimental data base available; and, integration of the ejector with complete aircraft configurations. Available prediction techniques are reviewed and performance of three ejector designs with vertical lift capability is summarized. Applications of the 'fuselage' and 'short diffuser' ejectors to fighter aircraft are related to current and planned research programs. Recommendations are listed for effort needed to evaluate installed performance.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-2629 , V/STOL Conference; Dec 07, 1981 - Dec 09, 1981; Palo Alto, CA
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    Experimental investigation of a jet inclined to a subsonic crossflow (1981)
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    Publication Date: 2019-07-13
    Description: Experimental investigations have been conducted to determine the surface-pressure distribution on a flat plate and a body of revolution with a jet issuing at a large angle to the free stream and to obtain a better understanding of the entrainment mechanism close to the jet exit by quantitative mean velocity surveys. Pressure data were obtained with a flat plate model at several nozzle injection angles using a single round nozzle. For the body of revolution model, data were obtained with a round jet exhausting perpendicular to the crossflow and with two round jets spaced two to six nozzle diameters apart. Mean velocity measurements were obtained with laser velocimeter surveys near the base of a round jet exhausting normal to a flat plate. For the flat plate model, the pressure field shifts downstream and the entrainment effect decreases with decreasing nozzle injection angle. For the body of revolution model with two jets, the jet-induced effect of the rear jet on the surface-pressure distribution was less than the front jet. The flow regions close to the jet are defined by the laser surveys, but further mean velocity surveys are required to understand the entrainment mechanism.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-2610 , V/STOL Conference; Dec 07, 1981 - Dec 09, 1981; Palo Alto, CA
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    A summary of V/STOL inlet analysis methods (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Methods to analyze the aerodynamic performance of V/STOL inlets at the NASA Lewis Research Center are discussed with emphasis on recent extensions and applications. Methods include the specification of the Kutta condition for a slotted inlet, the calculation of suction and tangential blowing for boundary layer control, and the analysis of auxiliary inlet geometries at angles of attack. An optimum diffuser velocity distribution is also developed, which can result in the shortest no-boundary layer control inlet and the lowest loss for the required amount of diffusion.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-2628 , V/STOL Conference; Dec 07, 1981 - Dec 09, 1981; Palo Alto, CA
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    The boundary layer on compressor cascade blades (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Some redesign of the cascade facility was necessary in order to incoporate the requirements of the LDA system into the design. Of particular importance was the intended use of a combination of suction upstream of the blade pack with diverging pack walls, as opposed to blade pack suction alone, for spanwise dimensionality control. An ARL blade was used to redo some tests using this arrangement. Preliminary testing and boundary layer measurements began on the double circular arc blades.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165079
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    Comparison of two parallel/series flow turbofan propulsion concepts for supersonic V/STOL (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The thrust, specific fuel consumption, and relative merits of the tandem fan and the dual reverse flow front fan propulsion systems for a supersonic V/STOL aircraft are discussed. Consideration is given to: fan pressure ratio, fan air burning, and variable core supercharging. The special propulsion system components required are described, namely: the deflecting front inlet/nozzle, the aft subsonic inlet, the reverse pitch fan, the variable core supercharger and the low pressure forward burner. The potential benefits for these unconventional systems are indicated.
    Keywords: AERODYNAMICS
    Type: NASA-TM-82743 , E-1056 , AIAA PAPER 81-2637 , V/STOL Conf.; Dec 07, 1981 - Dec 09, 1981; Palo Alto, CA; United States
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    Flag-lag-torsional dynamics or extensional and inextensional rotor blades in hover and in forward flight (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The differential equations describing the flap-lag-torsional motion of a flexible rotor blade including third-order nonlinearities were derived for hover and forward flight. Making use of the two boundary conditions, those equations were reduced to a set of three integro partial differential equations written in terms of the flexural deflections and the torsional variable.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165078
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